1) Field of the Invention
The present invention relates to an optical switching device and an optical member unit and, more particularly, to an optical switching device and an optical member unit suitably applicable to the case of switching over a destination for connection between each of optical fibers and the other such as the case of selecting an optical communication channel or the case where each of information devices connected with optical fibers switches over its companion for connection.
2) Description of the Related Art
Conventional M×N (M and N are integers greater than 1) optical switching devices include, for example, one described in the following Patent document 1. As shown in FIG. 16, Patent document 1 describes an optical switching device including incoming side optical fibers Fa1 to Fa4, outgoing side optical fibers Fb1 to Fb4, lenses La1 to La4 and Lb1 to Lb4, and mirrors M11 to M44 and a technique to switch over the connection between each of the incoming side optical fibers Fa1 to Fa4 and each of the outgoing side optical fibers Fb1 to Fb4 by the setting of the mirrors M11 to M44 for reflecting light beams.
However, in the configuration shown in FIG. 16, the distances between each of the incoming side optical fibers Fa1 to Fa4 and each of the outgoing side optical fibers Fb1 to Fb4 via the mirrors M11 to M44 are different from each another, and if an attempt is made to minimize the connection loss for a certain distance, the loss is increased for other distances and a dispersion of loss becomes great as the entire optical switching device.
In contrast to this, the technique described in Patent document 1 described above tries to solve the above-mentioned problem by employing a configuration as shown in FIG. 17. In the configuration shown in FIG. 17, 1×N optical switches sa1 to sa4 are connected to the incoming side optical fibers Fa1 to Fa4 respectively and, M×1 optical switches sb1 to sb4 are connected to the outgoing side optical fibers Fb1 to Fb4 respectively, each of the incoming side optical switches sa1 to sa4 is connected to the outgoing side optical switches sb1 to sb4 with optical fibers ff11 to ff44 respectively, and the distance traveled by light beams propagating in space is shortened by connecting the optical switches sa1 to sa4 and the optical switches sb1 to sb4 with the optical fibers ff11 to ff44, and thus an attempt is made to reduce the connection loss.
In Patent documents 2 to 5 described below also, an attempt is made to reduce a dispersion of loss as the entire optical switching device as described above.
In other words, as shown in FIG. 18, in an optical switch 100 described in Patent document 2, optical fibers 101 and 102 with converging optical transmission body 107 and 108 attached to the respective front ends thereof are arranged in such a manner that respective optical center axes 106 form a grid-like shape on the same plane and even when the optical fibers are switched over by a reflector 105, the distance between the optical fibers 101 and 102 with the convergent optical transmission media 107 and 108 attached to the respective front ends thereof is kept constant. Due to this, all of the optical path lengths between the end face of arbitrary one of the optically connectable optical fibers 101 and the end face of arbitrary one of the optically connectable optical fibers 102 are made equal to each another and thus the loss is kept constant.
Patent document 3 describes a 2-input & 2-output (2×2) optical switch 110 according to another conventional technique that makes the distance between each of incoming side optical fibers and each of outgoing side optical fibers constant as shown in FIG. 19. In the optical switch 110 shown in FIG. 19, reference numeral 111 denotes a flat substrate. Reference numeral 112 denotes four movable reflecting mirrors attached to the substrate 111 rotatably about a rotation axis 113 and the rotation axes 113 are arranged on the surfaces of the respective movable reflecting mirrors 112 so that the height thereof is the same, and the respective movable reflecting mirrors 112 are arranged so that the respective centers thereof are at respective vertexes of a rectangle.
In the optical switch 110, the paths of incident light beams 115 after reflection are switched over by changing the angle of the movable reflecting mirror 112 which the incident light beams 115 enter first and by which are reflected. In other words, when the movable reflecting mirror 112 is in a state of being rotated with respect to the substrate 111, the light beams 115 travels along an intersecting optical path 116 shown by a solid line and when in a state of being parallel to the substrate 111, the light beam 115 travels along a rectilinear optical path 117 shown by a broken line. When traveling along the intersecting optical path 116, the light beams 115 are reflected by an intersecting optical path reflecting mirror 114a arranged in parallel to the substrate 111 on the way, and are outputted as outgoing light beams. When traveling along the rectilinear optical path 117, the light beams 115 are reflected by a rectilinear optical path reflecting mirror 114b arranged in parallel to the substrate 111 on the way, and are outputted as outgoing light beams.
At this time, the optical path length of the intersecting optical path 116 and that of the rectilinear optical path 117 can be made equal by making a height hc of the intersecting optical path reflecting mirror 114a from the substrate 111 less than a height hb of the rectilinear optical path reflecting mirror 114b from the substrate 111. Due to this, the loss is kept constant regardless of the switching state.
In a 4×4 optical switch described in Patent document 4, the distance between each of incoming side optical fibers 126 and each of outgoing side optical fibers 127 is kept constant by employing such a configuration as shown in FIG. 20. The optical switch 120 has a substrate 121 having integrally 16 switch cells 125 formed of a MEMS, mirrors 122 and 123 perpendicular to a main surface 121A of the substrate 121 and in parallel to each other, and an optical unit 124 for providing input optical path P1 for input channels (input ports) #1 to #4 and an output optical path P2 for output channels (output ports) #1 to #4.
In this configuration, the switch cell 125 includes a switch mirror 128 provided movably with respect to the substrate 121, and switching over a first state in which the switch mirror 128 is parallel to the main surface 121A and a second state in which the switch mirror 128 is perpendicular to the main surface 121A allows the states of optical connection between each of the incoming side optical fibers 126 and each of the outgoing side optical fibers 127 to be switched over with an optical path formed by the collaboration of the mirrors 122 and 123. In this case, even when any one of the optical paths is formed, the distance between the optical fibers 126 and 127 can be made equal to, for example, the rectilinear distance between the optical fiber 126 at the input channel #4 and the optical fiber 127 at the output channel #1. In other words, by keeping the optical path length constant independent of the switching path, a loss fluctuation depending on the path is suppressed.
Moreover, in an optical switch 130 described in Patent document 5, as shown in FIG. 21, a first optical waveguide array 131 having n optical waveguides (#1, #2, . . . , #n) arranged so that the ends thereof are in an alignment and a second optical waveguide array 132 having m optical waveguides (#1, #2, . . . , #m) arranged so that the ends thereof are in an alignment are connected via an optical switch element 135 having n×m optical switches 135S arranged in a matrix on a substrate plane, light connecting optical elements 133 and 134, and first and second cata-dioptric elements 136 and 137, and the optical paths between the end of the i-th (i=1 to n) optical waveguide in the first optical waveguide array 131 and the end of the j-th (j=1 to m) optical waveguide in the second optical waveguide array 132 can be switched over arbitrarily.
In the optical switch 130, the first and second cata-dioptric elements 136 and 137 are arranged so that the optical path length between arbitrary one of the first optical waveguide array 131 and arbitrary one of the second optical waveguide array 132 is kept to a fixed length L0 (for example, the total of L1 to L4 in FIG. 21, which is the optical path length between the #n optical fiber constituting the first optical waveguide array 131 and the #m optical fiber constituting the second optical waveguide array 132) by deflecting the optical path between each of the first and second optical waveguide arrays 131 and 132 and the optical switch element 135, and thus a loss fluctuation depending on the path is suppressed.
[Patent document 1] Japanese Patent Laid-Open (Kokai) S54-038147
[Patent document 2] Japanese Patent Laid-Open (Kokai) S55-022723
[Patent document 3] Japanese Patent Laid-Open (Kokai) 2001-356283
[Patent document 4] Japanese Patent Laid-Open (Kokai) 2002-258177
[Patent document 5] Japanese Patent Laid-Open (Kokai) 2003-241239
However, the above-mentioned optical switches according to the conventional techniques described in Patent documents 1 to 5 have the following problems.
In the case of the optical switch described in Patent document 1 and shown in FIG. 17, the optical switches sa1 to sa4 and the optical switches sb1 to sb4 are connected with the optical fibers ff11 to ff44, therefore, there arises a problem in that the size is increased because the fibers need to be led circuitously, not linearly. Moreover, in order to realize the optical switches sa1 to sa4 and the optical switches sb1 to sb4, the optical fibers ff11 to ff44 need to be aligned, the optical fibers Fa1 to Fa4 and Fb1 to Fb4 need to be adjusted accurately to the positions of the optical fibers ff11 to ff44, etc., therefore, a problem arises in that the manufacture thereof requires a large amount of man-hours. Still moreover, if optical connectors are used for the connection between each of the optical switches sa1 to sa4 and sb1 to sb4 and each of the optical fibers ff11 to ff44, a number of connectors are required, whereby a problem arises in that the cost of the connectors is increased, the insertion loss due to the connector connection loss is increased, etc.
In the case of the optical switches 100, 110, 120, and 130 described in Patent documents 2 to 5 described above, in order to realize an N×N optical switch, N to the second power or more movable reflection means (for example, refer to reference numeral 105 in FIG. 18) are required, therefore, a problem arises in that the size of a movable reflection means is increased, the yield of the movable reflection means is likely to be reduced, the cost thereof is increased, etc.
Moreover, anyone of a plurality of optical paths formed by optical members interposed between optical fibers is made to be equal in length to the longest optical path.
At this time, the longer the optical path is, the greater the beam diameter needs to be, therefore, it is necessary to increase the diameter of an optical condensing means for condensing light beams outputted from optical fibers, and as a result, a problem arises in that the input/output fiber pitch is increased and the device is increased in size.
Still moreover, in the case of the optical switches 100 and 120 disclosed in Patent documents 2 and 4, the front ends of the respective fibers 101, 102, 126, and 127 need to be arranged obliquely, therefore, it is difficult to simultaneously manufacture optical fibers together in an array form. Because of this, the optical fibers need to be positioned and fixed one by one to assemble an optical switch and therefore a problem arises in that assembly requires a large amount of man-hours.
On the other hand, in the case of the optical switch 110 described in Patent document 3, it is necessary to make the height hc of the intersecting optical path reflecting mirror 114a from the substrate 111 differ from the height hb of the rectilinear optical path reflecting mirror 114b from the substrate 111, therefore, a special technique is required for the manufacture of the reflecting mirrors 114a and 114b and as a result, a problem arises in that the cost of the mirror is increased. Moreover, when an optical switch having a large number of inputs and outputs is configured, if the number of inputs and outputs is assumed to be N, substantially N×3 times of mirror reflection are required and as a result, a problem arises in that the yield is decreased, the cost of the mirror is increased, and the loss due to reflection is increased.